1. Field of the Invention
This invention relates to a device for guiding a continuously cast bar (called a strand) from the point it emerges from a casting wheel in which it has been cast, up to the point it enters an installation for processing the strand.
2. Background Information
Wheel type strand continous casting machines traditionally comprise a casting wheel having a trapezoidal or triangular shaped grooved periphery, a metal strip being applied to a section of the periphery so as to form a rotary mold.
The metal strip, produced in the form of an endless belt, is wound around return, pressure and tension pulleys which allow the metal strip to be applied to the portion of the wheel periphery forming the mold.
A feed chute supplying molten metal is arranged at one of the points where the metal strip breaks contact with the casting wheel.
Spraying booms are arranged in front of the metal strip around the wheel periphery allowing the rotary mold thus formed to be cooled.
A device in the form of a knife, called an extractor, is installed at the other point where the metal strip breaks contact with the casting wheel in order to take off the solidified metal strand from the wheel.
The form of this strand produced continuously by the casting machine, is identical to that of the casting wheel groove, save for shrinkage due to the cooling of the metal.
The strand so cast is thereafter directed to a processing installation comprising, for example, a rolling mill associated with tensioning devices and other elements.
In particular, when casting begins, the tip of the strand must pass into an automatic or non-automatic shearing machine located upstream of the processing installation and in order to eliminate through cutting into pieces of short lengths all that part of the strand whose metallurgical quality has not reached the level required to undergo the rolling transformations.
The automatic shearing device generally consists of a set of rollers-pinchers whose upper roller, or rollers, withdraw sideways to allow the strand to be lowered, and a rotary drum shear whose vertically-arranged axes allow the strand to be lowered between the knifes fixed onto the drums.
Once a reached meallurgical quality of the continuously cast strand has been reached, the rotary shear is stopped and the strand can then be directed to the rolling mill in which it is engaged in order to undergo successive continuous rolling operations, for example for the production of wire.
The operations of introducing the continuously cast strand into the shearing device and into the rolling mill are generally performed manually by operators who seize the strand with tongs as it leaves the casting wheel and guide it over the top of the wheel in order to introduce it into the shearing device or rolling mill located on the side facing the output of the wheel.
In a general way, since the curvature of the strand at the moment it leaves the wheel is the same as that of the wheel itself, the strand moves away from the extraction zone following a naturally curved path. The operator seizes the tip of the strand, makes it turn around the wheel and directs it to the input of the processing installation. Although the operator follows as much as possible the natural path of the strand, this maneuver calls for a fair amount of physical strength because of the stiffness of the strand, and for some alloys several operators must be present.
In addition, because the shearing machine and rolling mill are located a certain distance from the wheel, the weight of the strand over its path from the wheel to the shears becomes fairly substantial. A support table is therefore placed upstream of the shears to form a rolling path on which the strand can rest. The strand may also become tensioned as it passes through the pinching rollers, and so to prevent it from flattening against the casting wheel, the rolling path is extended up to above the wheel following a profile corresponding to the path naturally taken by the strand as it leaves the wheel.
Clearly such a maneuver is not without risk for operators.